Pulse TIG welding is similar to TIG welding, the max amperage is set and the output is controlled via the foot pedal. During welding, the pedal throttle is kept constant, but there may be slight adjustments required to add extra heat or to back off if there is too much heat.
The pedal press distance is directly related to the TIG torch output. When a pulsed waveform is the output rather than steady amperage, these same adjustments can be made. In this article, we will take a closer look at pulse TIG equipment, techniques, and troubleshooting to help you improve the process.
Understanding Pulse TIG Welding
Pulsed Gas Tungsten Arc Welding (GTAW) is commonly referred to as pulse TIG welding. For brevity and clarity, this is the term we will use in this article. This welding process utilizes a non-consumable tungsten electrode to create the arc for welding. It is a variant of traditional TIG welding, the main difference is the pulsing feature.
In traditional TIG welding, a constant current is applied to create a stable arc between the work piece and the tungsten electrode. But, in pulse welding the power is alternated between low background and high peak (pulse) current. This pulsing occurs at a frequency that’s typically measured in pulses per second (PPS). Controlling the intensity and duration of these two current levels will determine how the pulsing is achieved.
There are five main advantages of Pulse TIG Welding:
- Improved Control: Pulsing will improve control over the molten weld puddle which makes it easier to create accurate and consistent welds. This is especially true when the welder is working with thinner materials.
- Reduced Heat Input: The pulse parameters can be used to precisely control the heat input in the work piece. This is useful when materials that are sensitive to excessive heat are welded, the risk of heat affected zones (HAZ) and distortion are minimized.
- Improved Bead Appearance: Pulse TIG welding can be used to create beads with a ripple pattern that is aesthetically pleasing.
- Reducing Distortion: Working with improved control and lower heat input can minimize warping and distortion issues in the welded components.
- Increasing Productivity: With practice, pulse TIG welding has faster travel speeds than traditional TIG welding without sacrificing the weld quality.
Pulse TIG Welding Equipment
To use the pulse TIG welding process safely there are several tools, personal protection equipment (PPE,) and consumables required:
First Consideration is the Work Surface
- Ideally, this would be a welding table or other sturdy surface that’s free from contaminants.
- There must be a reliable source of power to deliver the necessary voltage and amperage to your TIG welding machine.
- The machine you choose should be capable of pulse welding with the materials and thicknesses you want to weld.
- A ground clamp is needed to create the electrical circuit and to ground the work piece.
- This will ensure that you have proper electrical conductivity throughout the welding process.
Safety should always be the priority during any welding process
- It’s important to wear the correct PPE when welding to promote safety and reduce the risk of injury.
- The welder should wear a welding helmet with a shade of 8-13 that’s suitable for TIG welding.
- In addition, the welder needs to wear safety glasses, a welding jacket, suitable footwear, and a good pair of welding gloves.
- Safety procedures should be followed carefully and shortcuts should be avoided.
TIG Welding Machine
At the business end of the TIG welding machine, we can find the TIG torch which is often referred to as the TIG gun. This component is used to control and hold the tungsten electrode and deliver the shielding gas to the weld area. This should be capable of handling the required amperage and be compatible with your TIG welding machine.
The non-consumable tungsten electrode will vary depending on the material you’re welding. There are four common types ceriated, lanthanated, pure tungsten, and thoriated. Welding filler rods may be required depending on the welding application to build up welds and fill gaps as needed.
Gas Regulator and Flow Meter
Two essential devices are the gas regulator and the flow meter. These control and measure the shielding gas flow from the attached gas cylinder to the TIG gun. The inert shielding gas prevents weld pool contamination from atmospheric contamination. There are a number of choices depending on the process specifications and welding materials. The two most common shielding gasses are argon or a helium-argon mixture.
Depending on the complexity of the project, you may need fingertip control or a foot pedal to make precise amperage adjustments. For high-amperage applications, you may want to consider a water-cooling system for the TIG gun and a tungsten grinder for electrode preparation. There may be a need for other consumables, such as collets, collet bodies, back caps, and gas cups to maintain the TIG torch depending on the specific machine and the welding frequency.
Techniques and Best Practices for Pulse TIG Welding
Pulse TIG welding offers improved control and precision, it’s a versatile alternative to traditional TIG welding, but specific techniques and best practices should be followed to create high-quality welds:
Preparation Before Starting Pulse TIG Welding
Proper preparation for Welding is essential, the work-piece should be clean and free from contaminants, such as grease, rust, dirt, oil, and others. The joint fit-up should be tight to reduce the need for excess filler metal and to make stronger welds. The tungsten electrode needs to be the correct type and size for the material you want to weld.
There are different tungsten types for specific welding applications and they should be sharpened to a fine point. The tungsten should be clean and free from contaminants to promote good arc stability. Before you start to weld, make sure you’re wearing appropriate PPE and that you have proper workplace ventilation to reduce exposure to fumes.
Starting the Weld
When you’re ready to start welding, set the right parameters on your TIG welding machine. The pulse frequency (PPS) should match the material and joint thickness requirements. As a rule of thumb, the higher frequencies are used to weld thinner materials and vice versa. The peak current controls penetration and the low current controls the heat input. Refer to the manufacturer’s recommendations for the shielding gas you’re using to select the optimal flow rate to protect the weld pool.
As you weld, hold the torch at the proper angle relative to the work-piece and joint. This is typically 15-20º from vertical, but it can vary depending on the specific application. The arc length between the electrode and work piece should be consistent. If the arc is too long, the bead appearance may be poor and the weld could be unstable. If the arc is too short, the electrode may stick and become welded to the work piece.
A steady travel speed is crucial for aesthetically pleasing and uniform weld beads. Pay close attention to the weld pool and the bead as you weld, and adjust the parameters as required. When you use filler rods feed them into the weld puddle and the correct speed and angle. The size and type of filler rod that you use should match the base material you’re welding.
Pulse TIG Process Success
The key to success with the pulse TIG process is the same as traditional TIG welding. This skill is easy to learn and hard to master. So, to gain valuable experience, it’s a great idea to practice the techniques you’ve learned with different materials and settings. Working on your weaknesses will stand you in good stead when you’re welding critical projects.
Ten common pulse TIG welding problems and how you can prevent them:
1/ An Inconsistent Weld Bead:
This typically manifests as irregular width or ripples that are usually caused by poor torch control or inconsistent travel speeds. The solution is to work on smoother torch control movements, the maintenance of a steadier travel speed and to check that the pulse parameters are correct.
2/ Excessive Spatter:
This is often caused by bad torch technique, contaminated filler rods, or incorrect pulse settings. Practice your torch technique, use cleaner filler rods, and properly adjust the pulse settings, and you can minimize spatter.
3/ Arc Instability:
This may occur if the torch angle is incorrect, the arc length is not consistently maintained or the pulse parameters are incorrect. To solve this issue keep the torch angle in the recommended range, keep the arc length consistent, and adjust the pulse parameters as needed.
4/ Tungsten Contamination:
This occurs when the tungsten electrode comes into contact with the work-piece if it’s dipped in the weld pool, and if the grinding is improper. This can be solved if the tungsten electrode is sharpened correctly with specific equipment for each material type and contact with the weld pool and work-piece is avoided.
5/ Incomplete Fusion:
Poor technique and insufficient heat can cause incomplete fusion and the weld will not penetrate the base material. To solve this, ensure that the joint fit-up is tight, increase the peak current, and slow your travel speed.
6/ Porosity:
Porosity can be caused by base material contamination and inadequate shielding gas coverage. These small pockets of gas inside the weld bead can weaken the weld joint. Cleaning and de-greasing the work piece, maintaining the correct torch angle, and protecting the weld pool with a consistent flow of shield gas can prevent porosity.
7/ A Lack of Fusion to the Root of the Joint:
This is typically caused by improper joint preparation and/or insufficient penetration. The solution is to make a precise joint fit-up and increase the peak current.
8/ Weld Cracking:
This can occur due to excessive heat input or rapid cooling and it’s typically found in the heat-affected zone (HAZ). To prevent cracks preheat the work piece and control the heat input using the peak and background current settings. If you’re welding materials that are prone to cracking use proper anneal or stress-relieving techniques to soften the metal.
9/ Undercutting:
This is a depression or groove at the weld bead edges that is usually caused by an incorrect torch angle or high currents. To fix this, adjust your torch angle, use the proper travel speed, and reduce the peak current.
10/ Crater Cracks and Arc Strikes:
This can occur if the arc is starting or ending in an inappropriate location on the work piece. To solve this issue don’t strike the arc on the base material, take care of where the arc is initiated and terminated, and use the proper crater fill technique.
Conclusion–Pulse TIG Welding
With practice, pulse TIG welding techniques can boost productivity significantly. But, to get the best out of this process it’s important to consider the joint design, materials, and TIG welding machine settings carefully. Practice is a requirement to gain proficiency, but the effort is worthwhile because this is a more versatile process than traditional TIG welding.
